In order to improve the fuel efficiency of an internal combustion engine (hereinafter referred to as “engine”), a valve opening/closing timing control device that controls the timing of opening/closing either one or both of an intake valve and an exhaust valve is conventionally used. A valve opening/closing timing control device of this type controls the opening/closing timing by changing the rotation phase of a driving rotating body that rotates in synchronization with a crankshaft, and a driven rotating body that rotates in synchronization with a camshaft, relative to each other. The driven rotating body of such a valve opening/closing timing control device is rotated along with the rotation of the driving rotating body, and also transmits rotative power to the camshaft. Therefore, studies have been performed to reduce the weight while maintaining the strength.
The valve opening/closing timing control device disclosed in Patent Document 1 has: a press-fitted portion that is press-fitted into a recessed portion that is formed in a driven rotating body; and is provided with a coupling member that couples the driven rotating body and a camshaft to each other. Such a press-fitted portion: has a plurality of fitting portions that are located at intervals along the rotation direction, and that engage with the inner circumferential surface of the recessed portion; and is configured such that the center line of at least one fitting portion orientated in the radial direction, out of the plurality of fitting portions, does not overlap partitioning portions in the radial direction.
The valve opening/closing timing control device disclosed in Patent Document 2 is provided with a coupling member that couples a driven rotating body and a camshaft to each other. The coupling member has: a flange portion that is inserted into a recessed portion formed in a driven rotating body; and a shaft portion that is inserted into a through hole that is formed in a camshaft-side wall member of a driving rotating body, and the outer diameter of the flange portion is set to be greater than the outer diameter of the shaft portion, and the flange portion is located between the driven rotating body and the wall member.
In the valve opening/closing timing control devices disclosed in Patent Documents 1 and 2, the driven rotating body is divided into a coupling member that requires strength and a rotating body that does not require strength, and the coupling member that requires strength is formed with a high-strength material. The coupling member and the rotating body are in contact with each other in a discontinuous manner, and the connection is realized with press-in force or the fastening force of a cam bolt. Oil channels are formed in the coupling member and the rotating body, and these oil channels are formed when the coupling member and the rotating body are in the state of being separated from each other, and are thereafter connected by positioning.
The valve timing adjustment device disclosed in Patent Document 3 includes: a vane rotor having a vane member that is housed in an accommodation chamber formed within a housing member so as to be rotatable relative to the housing member only within a predetermined angular range, and that partitions the accommodation chamber into an advancing chamber and a retarding chamber; and a boss portion that is formed with a material that is different from the material of the vane rotor, is embedded in the vane rotor, and is coupled to the other of a driving shaft and a driven shaft.
In the valve timing adjustment device disclosed in Patent Document 3, a boss portion made of an iron-based material is formed to envelop the vane rotor made of an aluminum-based material, by insert casting. The housing and the vane member are designed to ensure optimal clearance and airtightness of a fan-shaped space, and are reduced in weight in order to achieve a lightweight device. The oil channels that bring the boss portion and the vane rotor into communication with each other are individually formed when the boss portion and the vane rotor are in the state of being separated from each other, by positioning the oil hole of the boss portion and the oil hole of the vane rotor relative to each other.